The evidence is clear "and compelling" that Syrian President Bashar Assad's regime used chemical weapons against its own people last week, Secretary of State John Kerry told the American people Friday.

The U.S., Kerry said, knows where the rockets carrying the chemicals were fired from — territory controlled by the Assad regime — and when they were launched.

If a "thug and murderer" such as President Bashar Assad is allowed to do that without consequences, Kerry warned, there will be "no end to the test of our resolve. ... It matters if nothing is done."

In an appearance at the State Department, the secretary also said the death toll from that alleged chemical weapons attack was higher than has been reported. According to Kerry, U.S. intelligence has concluded that 1,429 people were killed. While he was speaking, the White House released some declassified details of what U.S. intelligence officials say they have learned about the attack.

Kerry indicated that a report about the attack from U.N. inspectors now in Syria won't affect the Obama administration's decision about how to hold Assad accountable. The U.N., he said, has stated that its investigators will only be able to determine whether chemical weapons were used — not who gave the order to fire them. What's more, Kerry said, "President Obama will ensure that the United States of American makes our own decisions ... on our own timelines based on our own values and interests."

There's an audio player at the top of this post. Click the play button to hear Kerry's statement.

As he spoke, we updated this post with highlights. Later this afternoon, President Obama is expected to offer some additional comments when he meets with some Baltic leaders at the White House.

Update at 1:25 p.m. ET. Question Is Not "What" Is Known, But What To Do:

Kerry finished his statement a few minutes ago. Toward the end, he said "the primary question is no longer what do we know." It is, "what we, collectively ... are going to do about it." As we said earlier, he did not give details about what the U.S. will do, but he was clearly making the case for a military response. Most analysts, NPR's Tom Bowman reports, believe it's likely there will be missile strikes on a few dozen military targets inside Syria.

Update at 1:15 p.m. ET. Being "Tired Of War" Does Not "Absolve Us Of Our Responsibility":

While acknowledging that the American people are "tired of war," Kerry says "fatigue does not resolve us of our responsibility." If the U.S. "turned a blind eye to a dictator's wanton use of weapons of mass destruction," Kerry said, the nation would be going against its own values.

Kerry does not offer any details about what type of military response there might be but says President Obama has pledged that it will be "limited and tailored."

Update at 1:11 p.m. ET. "Thug And Murderer":

Turning to why the U.S. must hold Assad accountable, Kerry says that if a "thug and murderer" is allowed to use chemical weapons against his own people, then other brutal dictators will do the same. "Make no mistake," he says, taking military action against Assad matters to U.S. and global security.

Update at 1:07 p.m. ET. From The Administration's Fact Sheet:

As Kerry speaks, the White House sends reporters a summary of the U.S. intelligence community's "assessment of the Syrian government's use of chemical weapons on Aug. 21, 2013."

It says, in part:

-- "The United States Government assesses with high confidence that the Syrian government carried out a chemical weapons attack in the Damascus suburbs on August 21, 2013."

-- "A preliminary U.S. government assessment determined that 1,429 people were killed in the chemical weapons attack, including at least 426 children, though this assessment will certainly evolve as we obtain more information."

-- "We have intelligence that leads us to assess that Syrian chemical weapons personnel – including personnel assessed to be associated with the SSRC – were preparing chemical munitions prior to the attack."